Method of producing half-tone plates.



PATENTED NOV. 19, 1907.

O. H. McINTOSH. METHOD OF PRODUCING HALF TONE PLATES.

APPLICATION FILED FEB. 21, 1907.

Inventor.

jwzw m Witnesses. Wm

i TEDSTATES ,CHARLES HAMILTON MCIXTOSH, OF MONTREAL, QUEBEC, CANADA.

PATENT OFFICE.

* I amnion F PRODUCING HALF-TONE PLATES.

lilo. 871,234;

To rilliwhoin it-mdy concern:

'ofiCanada, have-invented certain new and useful Im' rovements in Methods of Producing Halione Plates, of which the following is a specification.

Myinve'ntion relates to improvements in methods of fproducinghalf tone lates, and

lieapen thecost 0 production of good half tone plates by. the; elimination of the retching and" the ob'ect o the invention is to c hand toolingusual in. the finishing of the plate, and it consists essentially in the steps set, forth in detail in the present specification and particularly pointed out in the claims.

In the drawings, Figure 1 is a view of a a rectangular plate of glass having the exposed and developed film taken through the ordinary line screen laid out thereon. Fig.

2 is a view showing a plain negative taken without the intervening screen. Fig. 3 is a view showing the developed and stripped film of the screen negative plate laid over the plainnegative film and registering therewithas to the tives,

Itis wellknown in the art of.photo-enobject. appearing on the negagraving that the negative of the ob ect to be photographed and later to appear on the half tone plate is first taken on a wet plate through a plate of glass s eciall .prepared and which is usually ter'me a hail tone or line screen. This has the effect of producing the dots or relief necessary to effect a reproduction of the object from the half tone plate. It is necessary in order to faithfully print from the negative taken through the "screen following the reliminarv etching in theironbath, and it is with the elimination 'of the time necessaryto accomplish the re etching and hand tooling that this invention has to do.

" The common practice in the roduction ofhalf tones is first to prepare t 1e plate and Specification of Letters Patent.

- Application file l February 21.1907. Serial N 0. 358.600.

.plate of clear glass for r reproduce. the high lights and shadows to reetchand hand tool the metal plate, that'receives the Patented N 0v. 19, 1907.

the object to be photographed is taken without'the intervening screen and which hereinafter will be known as the plain negative while the first will be termed .the

screen negative for convenience in descri tion. Following the proper exposure of 't e plate for the "plain negative" and the subsequent development, the film is stripped from its glass plate an d laid 'on to a printing purposes. The film forming the "screen negative" which has been developed. is now stripped from its plate and laid over the film of the lain negative on the rinting glass plate a oresaid. The said film i firming the screen negative has completely therethroughout a re roduction of the lines and cross lines in the half tone screen and from these the necessai'y relief dots are obtained in the after steps of the method. It is'now essential that the screen negative shall register in every line of'the object photographed with the plain negative and 'to do this properly, the plain negative must have been sullieient .time on the printing'glass plate to adhere closely thereto and permit the moving of the screen negative over its surface by methods well known to those skilled in the art. The surface of the metal plate is then prepared in the usual manner and the registered films laced thereagainst and the whole inclosed III a frame and printed, then the metal plate is submerged in an iron bath as customary in the etchingstep of the usual half tone process.

under thescreen negative has the effect of bringing out the high lights and deepening the-shadows as the opacity of the lain negative at parts reduces the effect 0 the screen dots. on the screen negative and similarly the transparency of'some parts of the plain negative permits the clear exposure? of that fpart of the screen negative.

The acility with which the dots disappearin the preliminary 'etching'and which is the final etching in this method is remarkable and renders it quite unnecessary toreetch the metalplate-or hand tool it, and in fact it may be said that the first and final etching in this method is the final step beyond the ordinary cleaning up of the p ate. l u It may be advisable in the reproduction of some objects to superimpose the .plain negative on the screen negative on the The introduction of the plain negative printing glass, but the preferable way of carrying out my method is tosuperimpose the screen negative on the plain neg ative Further in some pictures in mak ing the plate for the reproduction of the same, it may improve the method herein described to have two or more plain negatives with a. screen negative or two or more screen negatives ivith plain negatives or a plurality of both, the feature of the invention being the combining of the plain negative with the usual half tone screen negative" in the operation of printing on to the prepared plate.

The order of the steps as herein set forth is not important in this process, except in so .far as necessity calls for the stripping of the films from the plates after the making of the negatives and .the etching subsequent to the printing on the metal, but the making of either one of the negatives before the -other is not important as also the stripping of either one of the films.

. \Vhat} claim as my invention is:

1. A method of producing half tone plat-es,

consisting in first fully exposing a late covered with a sensitive film to the oliject to be photographed through an intervening prepared screen and producing a screen negative, then exposing a plate covered with a sensitive film to the object to be photographed without having any "intervening screen and producing a plain negative, then stripping the screen negative of said object having all high lights, middle tones and shadows clearly shown from its plate, then superimposing the said screen negative on the plain negative and registering the lines of the object photographed of the one negative with the other, then preparing a metal plate, then printing the negatives so arranged on to said metal plate and finally submerging said prepared plate in a bath and etching, as specified.

2. A method of producing half tone plates,

consisting in first fully exposing a wet photographic plate to the object to be photo-v graphed through an intervening glass screen having lines arranged throughout its surface and -developing the same and producing the screen or half tone negative, then fully exposing a wet photographic plate to the object to be photographed without any intervening screen and developing said plate after exposure and producing the plain,

negative properly and clearly showing all details of the picture, then stripping the film of said plain negative from its plate and laying it on a transparent printing ase,

then strippingthe film of the screen negative" from its plate and laying it over the film forming the plain negative and regis- .tering the lines of the object photographed on the two films, thenpreparlng the metal plate, then printing the object photographed on the negativeson to the metal plate and finally etching by submersion, as specified.

3. In a. method of producing half tone plates, the superimposition of the fully exposed sereen negative on the fully exposed plain negative and the registration of the lines of the obiect photographed of the-one negative with the hnes of the other and the subsequent printing of the object photographed from the negatives so arranged, as specified.

Signed at the city of Montreal, in the District of Montreal, in the Province of Quebec, in the Dominion of Canada, this 14th day of February, 1907.

\ CHARLES HAMILTON MUINTOSH.

Witnesses: LLOYD BLACKMORE, ,G. H. TRESIDDER. 

